Allopodagrion brachyurum De Marmels, 2001

Neiss, Ulisses Gaspar, Fiorentin, Gelson Luiz & Marmels, Jürg De, 2011, The larva of Allopodagrion brachyurum De Marmels, 2001 (Odonata: Zygoptera: Megapodagrionidae) from Southern Brazil, Zootaxa 2836, pp. 44-50 : 45-48

Larva of Allopodagrion brachyurum De Marmels, 2001

(Figures: 2–21)

Exuviae slender, pale brown, with very long legs and rigid caudal gills as long as the body ( Fig. 2 ).

Head: subpentagonal in shape, with a ratio length/width of about 1.6, slightly wider than thorax and abdomen, with posterior margin concave. A very well developed, obtuse dorsal tubercle in sub-vertical orientation on each side of occiput, 0.8 mm in length, near postero-lateral margin (A in Fig. 3 and 4 ). Two small, blunt tubercles on top of head, between compound eyes (C in Fig. 4 ) and overlapping the lateral ocelli. Antenna 6-segmented, almost twice as long as head length, the first antennomere longest and with a diameter distinctly greater than the other antennomeres ( Fig. 5 ); fourth, fifth and sixth antennomeres furnished with thin, inconspicuous setae ( Fig. 6 ); third and fourth antennomeres darker than the others (in different exuviae can be the fourth and fifth). Labrum rounded and partially covering mandibles ventroapically and laterally ( Fig. 3 ). Prementum-postmentum articulation surpassing distal end of first coxae. Prementum with length/width ratio of about 1.4 (or width 0.66–0.68 times length), constricted at basal half, with dorsal surface bare; half of distal lateral margins furnished with 10–12 thin setae ( Fig. 7 ); ligula little convex, finely crenulated with blunt denticles ( Fig. 8 ); median cleft well marked and deep, sides parallel; a small blunt tubercle on each side of median cleft slightly proximal to distal margin ( Fig. 8 ). Distal margin of labial palps with three pointed teeth, median one longest. A group of six to nine short spines on outer margin of palp, close to the insertion of movable hook ( Fig. 8 ). Inner margin of labial palps finely crenulated ( Fig. 8 ). Mandibles two-branched ( Fig. 9 ): L 1’1234 0 a(m12345)b, R 1’1234 y a(m0)b. Maxilla with three long, curved teeth on the inner side; apical tooth with three supplementary teeth ( Fig. 10 ).

Thorax: with a wide dark lateral line from anterior margin of prothorax to base of wing pads. Prothorax rather elongate, quadrangular, with angles rounded and with median lateral tubercle (B in Fig. 3 ). Hind wing pads surpassing the end of S4; fore wing pads reaching distal half of S4. Legs extremely long, especially those of meso- and meta-thorax, all unpatterned. Hind femur surpassing end of S7, in one specimen S8 (probably reaching S 9 in F-0 larvae). Femora and tibiae glabrous, except apex of femora furnished dorsally with small group of rather long setae partly overhanging the femur-tibia articulation ( Fig. 11 ). Ventral side of apex of tibia covered by rigid setae. Tarsus 3-jointed, all with 2 rows of peculiar ventral spines armed with small denticles ( Fig. 12 ); tarsal claws moderately long, thin and acute.

Abdomen: tergites with short and minute setae, which are longer and more abundant on lateral and posterior margins; without dorsal or lateral hooks or spines. S10 with posterior dorsal margin elevated in middle. Female gonapophyses surpassing distal end of S10, external lobes with setae and small spines on outer side ( Fig. 18 ). Male gonapophyses small and triangular, covered with numerous short spines and slightly surpassing distal end of S9 ( Fig. 19 ). Caudal gills extremely long and stiffened ( Fig. 13 ), lateral ones as long as body and triquetral; triangular in cross-section ( Fig. 16 ); mid-dorsal gill cross shaped in cross-section ( Fig. 17 ), shorter than lateral ones ( Fig. 13 ), but longer than abdomen. Longitudinal carinae of all gills with small spines along their entire length, increasing in size in antero-posterior direction and with intercalated long and thin setae distally, mainly in median gill ( Figs. 14 and 15 ). Female cercus conical ( Fig. 20 ); male cercus with apex rounded ( Fig. 21 ).

Measurements (in mm; females N = 1, males N = 3): Larval size without gills, female 16.7, males 16–17.4; head length, female 2.1, male 1.9; head width, female 3.4, male 3.2–3.3; antenna, female 3.4, male 3.3; prementum length, female 2.7, male 2.4–2.5; prementum max. width, female 1.8, male 1.6–1.8; hind wing pads, female 5.5, male 5.1–5.2; fore wing pads, female 5.7, male 5.5–5.6; femur, female F1 6, F2 6.7, F3 7.7, male F1 5.7, F2 7.3, F3 7.7–8; tibia, female T1 7.5, T2 9.2, T3 10.1, male T1 6.7, T2 8.5–8.8, T3 9.8–10.1; cercus, female 0.3, male 0.6; dorsal caudal gill, female 15.4, male 14.5–14.7; lateral caudal gill, female 17.2, male 16.6–17.3.

Material. BRASIL: RIO GRANDE DO SUL: Caraá: balneário João Fernandes, Rio dos Sinos, larvae found among roots at the stream margin (29º 45' 50.4''S; 50º 25' 39.6''W; 55 m. a.s.l.), 2ɗ exuviae (last-instar larvae collected in 06.x.1995 emerged on 02.xi.1995 and 03.xii.1995); 1Ψ exuvia (last-instar larva collected in 06.x.1995 emerged on 27.x.1995); 1ɗ exuvia (last-instar larva collected in 16.vii.1999 emerged on 24.xi.1999). All specimens were collected by G. L. Fiorentin and R. J. Altenhofen.

Figures

FIGURE 2. Exuvia of Allopodagrion brachyurum (Odonata: Megapodagrionidae), female, in dorsal view (reared in laboratory). (Scale bar: 5 mm).

FIGURE 3. Exuvia of Allopodagrion brachyurum (Odonata: Megapodagrionidae) female: head and prothorax, in ventro-lateral view. Arrows: A) well developed sub-vertical blunt tubercle on each side of occiput, B) median lateral tubercle of prothorax.

FIGURES 4 – 12. Allopodagrion brachyurum (Odonata: Megapodagrionidae), exuviae (Ƥ, 3): 4) head, in dorsal view, “ A ” and “ C ” indicate dorsal and occipital blunt tubercles; 5) antenna; 6) last three antennomerous; 7) prementum, dorsal view; 8) Labial palp and ligula, dorsal view; 9) left (L) and right (R) mandibles, inner side; 10) maxila, dorsal view; 11) Femur apex, dorsal view; 12) peculiar spine of tarsus. (Scale bar: 1 mm; Fig. 12: 25 – 30 µm).

FIGURES 13 – 21. Allopodagrion brachyurum (Odonata: Megapodagrionidae), exuviae (Ƥ, 3): gills: 13) left lateral and middorsal, 14) distal fourth portion, 15) proximal fourth portion, 16) lateral in cross-section, 17) mid-dorsal in cross-section; 18) female gonapophyses; 19) male gonapophyses; 20) female cercus; 21) male cercus. (Scale bar: 1 mm).